A boot band is used, for example, to clamp a boot that covers the power transmission of an automobile, so that (1) internal grease and the like are prevented from flowing out from the boot, and (2) water and foreign matter are prevented from infiltrating into the boot. Also, because the boot band is used to clamp the member to be clamped under the condition that the boot band is wound around the member to be clamped, one pair of boot-band pawls are provided on the boot band so that a clamping tool can be hooked onto the boot-band pawls to clamp the boot band.
FIGS. 11 and 12 show a first conventional boot band 1 (see Patent Document 1), and FIGS. 13 and 14 show a second conventional boot band 2 (see Patent Document 2). The boot band 1 or 2 consists of a band body 3 made of a thin metallic sheet, and is wound in a ring-like form so as to clamp the member in such a way that the boot band is wrapped completely around the member to be clamped. Therefore, when the band body 3 is wound (around the member to be clamped), the winding is done in such a way that the outer-layer portion of the band body 3 overlaps the inner-layer portion of the band body 3. Therefore, an outer layer portion 4 and an inner-layer portion 5 are formed.
In the first conventional boot band 1, a first boot-band pawl 6 is formed on the outer-layer portion 4, and a second boot-band pawl 7, which forms a pair with the first boot-band pawl 6, is formed on the inner-layer portion 5. Engagement holes 8 and 9 are formed in the area between the first boot-band pawl 6 and the end (free end) of the outer-layer portion 4. The engagement hole 8 is longer than the engagement hole 9, and the engagement hole 8 is also used as a temporary-tacking hole for temporarily tacking the band body 3. A second boot-band pawl 7, a temporary-tacking hook 10, and engagement pawls 11, 12 are sequentially arranged on the inner-layer portion 5 of the boot band 1 in the lengthwise direction of the band body 3 (in the clockwise direction in FIG. 11).
After the boot band 1 is wound like a ring as shown in FIG. 11, the second boot-band pawl 7 and the temporary-tacking hook 10 are inserted into the engagement hole 8 of the outer-layer portion 4. Then, clamping tools (not shown) are hooked onto a pair of the boot-band pawls 6 and 7, and the boot-band pawls 6 and 7 are pressed toward each other in such a way that the distance between the boot-band pawls 6 and 7 shortens, so that the diameter of the ring-like band body 3 is reduced. The arrows F in FIG. 12 indicate the directions of clamping. By this pressing, the engagement pawl 11 is inserted into and engaged with the engagement hole 8, and the engagement pawl 12 is inserted into and engaged with the engagement hole 9, so that a clamping condition—whereby the diameter of the boot band is reduced—is achieved.
At this time, there is a space between the end section (i.e., the section near the engagement hole 9) of the outer-layer portion 4 and the inner-layer portion 5. The top of the end section of the outer-layer portion 4 is pressed from its outer peripheral side toward the center of said ring-like form. While maintaining such a pressed condition, the engagement pawl 12 is engaged with the engagement hole 9 so as to achieve final clamping.
As shown in FIGS. 13 and 14, in the second conventional boot band 2, a first boot-band pawl 21 is formed on the top- and toward the end of the outer-layer portion 4, and a second boot-band pawl 22, which forms a pair with the first boot-band pawl 21, is formed on the inner-layer portion 5. Also, the first boot-band pawl 21 and engagement holes 23, 24, and 25 are sequentially formed on the outer-layer portion 4 along the lengthwise direction of the band body 3 from the first boot-band pawl 21 side (in the counterclockwise direction in FIGS. 13 and 14), and engagement holes 26, 27, and 28 corresponding to these engagement holes 23, 24, and 25 are formed on the inner-layer portion 5.
The second boot-band pawl 22 is press molded so as to rise outward in the radial direction, and an engagement hole 22a, which opens toward the first boot-band pawl 21, is formed in the second boot-band pawl 22. Also, the top end (free end) of the first boot-band pawl 21 of the outer-layer portion 4 serves as a terminal end 29 that extends in a flat form and that is inserted into the second boot-band pawl 22 through the engagement hole 22a. 
As shown in FIG. 14, the band body 3 is placed—in a ring-like form—onto the member to be clamped so as to clamp the second conventional boot band 2 around the member to be clamped. Under this condition, a pair of pawls 15a and 15b of a clamping tool 15 are hooked and locked onto the boot-band pawls 21 and 22, so that the boot-band pawls 21 and 22 are pressed toward each other in the directions shown by arrows F, and whereby the diameter of the boot band is reduced. At the time of such pressing, while the terminal end 29 is inserted—in the direction shown by the arrow F—into the engagement hole 22a, the engagement pawls 26, 27, and 28 are engaged with their corresponding engagement holes 23, 24i and 25, thus achieving a clamping condition.
Patent Document 1: Specification of U.S. Pat. Re. No. 33744
Patent Document 2: Publication of Japanese Patent No. 3001266
In the first conventional boot band 1, shown in FIGS. 11 and 12, it is necessary that a load be applied onto the band body 3 in the circumferential direction by using a clamping tool, that the outer-layer portion 4 be pressed inward while maintaining the above-mentioned loading condition, and clamping be done while maintaining the above-mentioned pressing condition. As such, two actions—one in the circumferential direction, and one inward—are necessary at the time of clamping, which makes the clamping operation troublesome. In addition, because two actions are necessary, there is the following problem: the time needed for a clamping operation is needlessly long, which adversely impacts workability.
In contrast, in the second conventional boot band 2, shown in FIGS. 13 and 14, because the terminal end 29 is inserted into the engagement hole of the second boot-band pawl 22, the operation of pressing the outer-layer portion 4 inward is not necessary. Therefore, clamping can be performed by only one action, and clamping workability is improved in comparison with that of the first conventional boot band 1.
However, in the case of the boot band 2 shown in FIGS. 13 and 14, the inner-layer portion 5 might buckle at the time of clamping.
FIG. 15 shows how such buckling 19 can occur. When clamping pressure is applied to the pair of boot-band pawls 21 and 22, the outer-layer portion 4 of the boot band 2 slides in the direction in which the load is applied. By this sliding, the outer-layer portion 4 climbs over the engagement pawl 26 of the inner-layer portion 5. However, at the time of this climbing over, the outer-layer portion 4 is hooked onto the top part of the engagement pawl 26, with which it becomes locked. By this locking, a load—which originally is to be used in sliding the outer-layer portion 4 and reducing the diameter of the boot band—is applied, via the outer-layer portion 4, onto the engagement pawl 26 of the inner-layer portion 5.
Thus, even when a load is applied onto the pair of boot-band pawls 21 and 22, the condition becomes the same as that when the load is being received between the second boot-band pawl 22 and the engagement pawl 26 of the inner-layer portion 5. When the clamping load on the band body 3 exceeds the buckling-resistance capability of the band body 3, buckling 19 occurs on the boot band 3 between the second boot-band pawl 22 and the engagement pawl 26 of the inner-layer portion 5.
FIG. 16 shows a countermeasure to prevent such buckling 19. That is, the distance L1 between the engagement pawl 26 of the inner-layer portion 5 and the first boot-band pawl 21 of the outer-layer portion 4 is made to be long. As a result, the terminal end 29 at the tip of the outer-layer portion 4 can clamp the inner-layer portion 5 while pressing that inner-layer portion 5 from the outside. Thus, buckling of the inner-layer portion 5 is prevented, and insertion of the terminal end 29 into the engagement hole of the second boot-band pawl 22 is facilitated.
However, because when the countermeasure shown in FIG. 16 is taken, the distance L1 between the engagement pawl 26 of the inner-layer portion 5 and the first boot-band pawl 21 of the outer-layer portion 4 is long, the overlapping portion between the outer-layer portion 4 and the inner-layer portion 5 also must be long, resulting in a need for a longer band body 3. As a result, the following problems arise: (1) the boot band becomes heavy, (2) its cost increases, and (3) there is limitation as to how much the diameter of the band can be reduced.